2. N. sessiliflòrum, Nutt. Stems erect, rather simple; _leaves obtusely incised_ or toothed, obovate or oblong; _flowers minute, nearly sessile_; pods elongated-oblong (5--6´´ long), thick; style very short.--W. Ill. to E. Kan., Tenn., and southward. April--June. 3. N. obtùsum, Nutt. Stems much branched, diffusely spreading; _leaves pinnately parted or divided_, the divisions roundish and obtusely toothed or repand; _flowers minute, short-pedicelled; pods longer than the pedicels_, varying from linear-oblong to short-oval; style short.--With n. 1 and 2. 4. N. palústre, DC. (MARSH CRESS.) Stem erect; _leaves pinnately cleft or parted_, or the upper laciniate; the lobes oblong, cut-toothed; _pedicels about as long as the small flowers and mostly longer than_ the oblong, ellipsoid, or ovoid _pods_; style short.--Wet places or in shallow water; common. June--Sept.--Flowers only 1--1½´´ long. Stems 1--3° high.--The typical form with oblong pods is rare. Short pods and hirsute stems and leaves are common. Var. HÍSPIDUM is a form with ovoid or globular pods. (Eu.) § 3. _Petals white, much longer than the calyx; pods ovoid or globular; leaves undivided, or the lower ones pinnatifid; root perennial._ 5. N. lacústre, Gray. (LAKE CRESS.) Aquatic; immersed leaves 1--3-pinnately dissected into numerous capillary divisions; emersed leaves oblong, entire, serrate, or pinnatifid; pedicels widely spreading; _pods ovoid, 1-celled, a little longer than the style_.--Lakes and rivers, N. E. New York to N. J., Minn., and southwestward. July--Aug.--Near N. amphibium. N. ARMORÀCIA, Fries. (HORSERADISH.) Root-leaves very large, oblong, crenate, rarely pinnatifid, those of the stem lanceolate; fruiting pedicels ascending; _pods globular_ (seldom formed); _style very short_. (Cochlearia Armoracia, _L._)--Roots large and long; a well-known condiment. Escaped from cultivation into moist ground. (Adv. from Eu.) 12. BARBARÈA, R. Br. WINTER CRESS. Pod linear, terete or somewhat 4-sided, the valves being keeled by a mid-nerve. Seeds in a single row in each cell, marginless. Cotyledons accumbent.--Mostly biennials, resembling Nasturtium; flowers yellow. (Anciently called the Herb of St. Barbara.) 1. B. vulgàris, R. Br. (COMMON WINTER CRESS. YELLOW ROCKET.) Smooth; lower leaves lyrate, the terminal division round and usually large, the lateral 1--4 pairs or rarely wanting; upper leaves obovate, cut-toothed, or pinnatifid at the base; pods erect or slightly spreading; or in var. STRICTA, appressed; in var. ARCUÀTA, ascending on spreading pedicels.--Low grounds and roadsides; apparently introduced, but indigenous from L. Superior northward and westward. (Eu.) B. PRÆ̀COX, R. Br. (EARLY WINTER C.), with 5--8 pairs of lateral lobes to the leaves, and longer pods on very thick pedicels,--yet probably only a variety of the other,--somewhat cultivated from N. Y. southward as a winter salad, under the name of SCURVY-GRASS,--is beginning to run wild. (Eu.)